1. Field of the Invention
The present invention relates to a silica-supported catalyst used in the production of an unsaturated nitrile.
2. Description of the Related Art
A method in which propylene or isobutylene is subjected to a vapor-phase catalytic oxidation or vapor-phase catalytic ammoxidation reaction to produce a corresponding unsaturated carboxylic acid or unsaturated nitrile is conventionally well known. In recent years, attention has been directed to a method which subjects propane or isobutane instead of propylene or isobutylene to a vapor-phase catalytic oxidation or vapor-phase catalytic ammoxidation to produce the corresponding unsaturated carboxylic acid or unsaturated nitrile. Consequently, as a catalyst for vapor-phase catalytic ammoxidation of propane or isobutane, a variety of oxide catalysts have been proposed.
Patent Literature 1 discloses a silica-supported catalyst having an increased pore volume as a result of using a silica sol and silica powder as silica raw materials.
Patent Literature 2 discloses a composite oxide catalyst used when producing an acrolein or acrylic acid, which has a pore distribution adjusted to a specific range.
Patent Literature 3 discloses a granular porous ammoxidation catalyst in which the pores are controlled to within a specific range in order to improve the yield of the target product.    Patent Literature 1: Japanese Patent Laid-Open No. 2002-219362    Patent Literature 2: Japanese Patent Laid-Open No. 2003-220334    Patent Literature 3: International Publication WO 2004-078344